I have low expectations, if at all.
Having spent 3 or 4 times as much on shoddy mods that lasted less than a year (less than 6 months with joyetech EVIC) I'll be happy with even 4 months.
The whole idea that buying a mod with replaceable batteries is better is kind of flawed. OK, so the batteries will last x amount of charges, but chances are the mod won't go on forever, few do.
The iStick is essentially a throwaway item. Under 3 months, not many people are going to be happy.More than 6 makes it a bargain in my eyes.
With that in mind, I highly suggest you check out REO Mods. My reo is just as stable today as it was when I got it. So is the RM2 I picked up.
Keep in mind that means wrapping coils, so study up on that.
Or just go with a mechanical mod, just a battery and mechanical switch, and do tanks.